In a long-term postoperative study of patients undergoing septal myotomy-myectomy for hypertrophic cardiomyopathy, operative mortality was 8%. With 1 exception, all surviving patients experienced considerable symptomatic benefit. Although 10% of the patients died late postoperatively (1.8%/year) and 12 percent subsequently developed severe recurrent symptomatic limitation, the large majority (70%) maintained their improved symptomatic status. These findings confirmed our belief that operation should be offered to patients with obstructive hypertrophic cardiomyopathy who have symptoms that do not respond adequately to medical therapy.